<!DOCTYPE html>
<html lang="en">

<head>
    <meta charset="UTF-8" />
    <meta name="viewport" content="width=device-width, initial-scale=1.0" />
    <title>Three Equal Divs</title>
    <style>
        .container {
            display: flex;
            flex-direction: column;
            height: 500px;
        }
        
        .box {
            flex: 1;
            height: 100px;
        }
        
        .box1 {
            background-color: red;
        }
        
        .box2 {
            background-color: green;
        }
        
        .box3 {
            background-color: blue;
        }
    </style>
</head>

<body>
    <div class="container">
        <div class="box box1"></div>
        <div class="box box2"></div>
        <div classdiv class="box box3"></div>
    </div>
</body>

</html>